This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-6127, filed Jan. 15, 2001, No. 2001-309800, filed Oct. 5, 2001; and No. 2001-363082, filed Nov. 28, 2001, the entire contents of all of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a power supply system, and more particularly to a power supply system applicable as a portable power supply system and having a power generation function capable of effectively utilizing an energy resource to generate, and to an electric device provided with the power supply system.
2. Description of the Related Art
In all household and industrial fields, various kinds of chemical cells are used. For example, a primary cell such as an alkaline dry cell or a manganese dry cell is often used in watches, cameras, toys, and portable acoustic devices, and it has a characteristic that its quantity of production is large from the global viewpoint and it is inexpensive and readily available.
A secondary cell such as a lead storage battery, a nickel-cadmium storage battery, a nickel-hydrogen storage battery, a lithium ion battery is often used in mobile phones or personal digital assistances (PDA) which are in widespread use in recent portable devices such as a digital video camera or a digital still camera, and it has a characteristic which is superior in the economical efficiency because it can be repeatedly charged and discharged. Among secondary cells, the lead storage battery is utilized as a start-up power supply for vehicles or marine vessels or an emergency power supply in industrial facilities or medical facilities and the like.
In recent years, with the rising interest in environmental concerns or energy problems, problems concerning waste materials generated after use of chemical cells such as described above or those concerning the energy conversion efficiency have come under close scrutiny.
The primary cell has its inexpensive product price and is readily available as described above, and there are many devices which utilize this cell as a power supply. Further, basically, when the primary cell is once discharged, the battery capacity can not be recovered, namely, it can be used only once (which is a so-called disposable battery). A quantity of waste materials per year, therefore, exceeds, several millions tons. Here, there is static information mentioning that a ratio of the entire chemical cells which are collected for recycling is only approximately 20% and remaining approximately 80% is thrown away in the natural world or subjected to landfill disposal. Thus, there is fear of environmental destruction and disfigurement of the natural environment by heavy metal such as mercury or indium included in such uncollected batteries.
Verifying the above-described chemical battery in the light of the efficiency of use of an energy resource, since the primary cell is produced by utilizing the energy which is approximately 300-fold of the dischargeable energy, the efficiency of use of the energy is less than 1%. Even in case of the secondary cell which can be repeatedly charged and discharged and is superior in the economical efficiency, when the secondary cell is charged from a domestic power supply (convenience outlet) or the like, the efficiency of use of the energy drops to approximately 12% due to the efficiency of power generation in an electric power plant or the transmission loss. Therefore, it can not be said that the energy resource is necessarily efficiency utilized.
Thus, the attention is recently drawn on various kinds of new power supply systems or power generation systems (which will be generically referred to as a xe2x80x9cpower supply systemxe2x80x9d hereinafter) including a fuel battery which has less influence (burden) on the environment and is capable of realizing the extremely high energy utilization efficiency of, e.g., approximately 30 to 40%. Furthermore, for the purpose of application to a drive power supply for vehicles or a power supply system for business use, a cogeneration system for domestic use and others, or substitution for the above-described chemical cell, study and development for practical application are carried out extensively.
In the future, however, in order to reduce the size and weight of a power supply system having a high energy utilization efficiency such as a fuel cell and apply this system as a substitute (compatible product) for a transportable or portable power supply, for example a chemical cell as described above, there are following problems.
Specifically, for example, in an existing chemical cell, basically, since a predetermined voltage and an electric current are supplied and a load can be driven by only connecting positive and negative electrode terminals to the load, there is an advantage that such a chemical cell can be easily handled.
On the contrary, since most of the power supply systems having the high energy utilization efficiency including a fuel cell basically have a function as power generating means using a predetermined power generation fuel (for example, a power generator which directly or indirectly converts the chemical energy of the fuel into electric power), they are largely different from the above-described chemical cell in the structure or the electrical characteristic.
That is, in the power supply system, as similar to the general-purpose chemical cell, predetermined electric power can not be supplied or shut off by only connecting or disconnecting the electrode terminals (terminals corresponding to the positive electrode terminal and the negative electrode terminal in the general-purpose chemical cell) used for supplying electric power with respect to the load. Therefore, the power supply system disadvantageously requires a complicated structure or control processing in order to drive or stop the load and the power supply system. Further, in case of applying such a power supply system as a portable power supply, since a quantity of the power generation fuel which can be carried or transported is restricted, the power generation fuel must be controlled to be efficiently consumed and the operating time (duration of life) as the power supply system must be further prolonged.
According to the present invention, a power supply system which generates predetermined electric power by using a power generation fuel can be easily handled by connecting a load with an electrode terminal directly, as similar to the general-purpose chemical cell. Also, in the present invention there are advantages that loss of the power generation fuel may be controlled, thereby improving the utilization efficiency of an energy resource and making the operating time more prolonged.
The power supply system according to the present invention, to obtain above-mentioned advantages, uses the power generation fuel and generates supply electric power, and comprises at least a fuel charged portion in which the power generation fuel is charged, power generating means for generating the supply electric power by using the power generation fuel supplied from the fuel charged portion and including a fuel reforming type fuel cell for example, output controlling means for operating or stopping the power generating means, start-up controlling means for supplying start-up electric power used for operating the output controlling means to the output controlling means.
The start-up controlling means supplies electric power independent from the operation of the power generating means to the output controlling means as the start-up electric power at the time of starting up the power generating means, and supplies electric power based on the power generation electric power generated by the power generating means to the output control portion as the start-up electric power after starting up the power generating means. The start-up controlling means may include a primary cell which holds predetermined electric power independently from the operation of the power generating means as the start-up electric power or a start-up power supply portion which holds the electric power charged and held by the electric power supplied from outside, and supplies the electric power to the output controlling means as the start-up electric power at the time of starting up the power generating means. In addition, the start-up controlling means may include an auxiliary electric power holding portion which charges a part of the power generation electric power generated by the power generating means, and supplies charge electric power of the auxiliary electric power holding portion to the output controlling means as the start-up electric power after starting up the power generating means.
Hereby, the operation in the power supply system which generates supply electric power by using the power generation fuel may be controlled by a simple control to perform or stop the operation of the power generation means, and the cost of the power supply system can be decreased. Only at an initial stage of the start-up operation in the power generation means, the start-up electric power is supplied from the start-up power supply portion. Then, the power generating operation is kept by supplying the feedback electric power based on the power generating electric power as the start-up electric power, thereby performing the start-up operation excellently for a long period by using a primary cell having very small capacitance as the part of the start-up power supply portion.
Furthermore, the power supply system which generates supply electric power by using the power generation fuel according to the other aspect of the present invention comprises at least, in an electric power generation portion, electric power holding means for holding electric charge based on the power generation electric power generated by the power generating means, supply electric power generating means for generating the supply electric power based on held electric power held in the electric power holding means, system controlling means for controlling operation or stop of the power generating means and charge or stop of the electric power holding portion in accordance with a change of the held electric power.
Hereby, the operation of the power supply system can be controlled only for operation or stop of the power generation means according to a condition of held electric power held in the electric power holding means, thereby simplifying the construction and the operation control of the device. Also, in the operation of the power supply system, constant supply electric power may be output based on the electric power held in the electric power holding means kept under predetermined pressure, and so unnecessary power generation operation of the power generation means may be avoided and loss of the power generation fuel may be controlled, thereby improving the energy utilization efficiency highly. As result, the present invention provides the power supply system that can operate for a long time.
Furthermore, the present invention may apply as the electric power holding means a structure that is constituted by one or more capacitance elements, or a structure in which a plurality of capacitance elements are connected with a predetermined relationship, for example a structure that is able to switch the connection in series or in parallel.
Hereby, in comparison with the case applying as the electric power holding means the general-purpose secondary cell and the like, the weight of the device can be decreased remarkably, and the load which is connected to the power supply system may be driven by the supply electric power based on the held electric power. Thereby, even if driving condition changes rapidly, constant electric power may be supplied relatively. Also, even if the power generation fuel is consumed absolutely and so the fuel charged portion is removed and changed to another one, the electric power stored in the electric power holding portion can be output constantly for a moment, thereby keeping the generation of supply electric power and then the driving of the load.
In addition, in the power supply system according to the present invention, the whole power supply system or at least the fuel charged portion may be detachably constituted with respect to the electric device which includes the load operating by supply electric power supplied from the power supply system. The fuel charged portion is detachably constituted with respect is to the electric power generation portion.
The electric power generation portion is modularized for example. The electric power supply portion has the physical outer profile that is constituted to have size and dimensions equivalent to one of different general-purpose chemical cells, and has a double-electrode terminal structure.
Hereby, when the power generation fuel charged in the fuel charged portion is consumed or decreased, the fuel charged portion may be removed from the power generation portion and changed to new fuel charged portion. As a result, it is possible to use the power generation module constantly, and to simply use the whole power supply system or the fuel charged portion like general-purpose chemical cell. The change and recovery of the fuel charged portion will be possible, and so in the whole power supply system a waste amount may be decreased. In the outer profile, also, the high compatibility with the general-purpose chemical cell may be kept, whereby the power supply system that has very high energy conversion efficiency can be popularized in the existing market of the chemical cell, without difficulty.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.